Welcome to the new version of the Patents Manual. Please note there are changes to the numbering and sequence of the chapters and pages in the manual. You are encouraged to take the time to explore and familiarise yourself with this new structure. Rule 91 Obvious Mistakes in Documents

Date Published

Key Legislation:

Administrative Instructions under the PCT:

  • s607 Rectifications of Obvious Mistakes under Rule 91

Regulations under the PCT:

PCT ISPE Guidelines:

  • Chapter 8 Rule 91 – Obvious Mistakes in Documents 

Rule 91.1 provides that obvious mistakes may be rectified. A request for rectification will be in the form of a letter from the applicant. Where a request for rectification in respect of any document other than the request form is submitted to the International Preliminary Examining Authority, PCT Unit will forward the request for rectification, the relevant file and necessary forms to the relevant examination unit for consideration. [Rule 91.1 PCT/GL/ISPE/12 at Chapter 8]

The search examiner considers whether the mistakes are rectifiable under Rule 91.1 and gains agreement from a senior examiner. The examiner then completes form PCT/IPEA/412 inserting the name of the senior examiner consulted as "Authorised Officer" and the examiner clicks Submit Task in RIO.


  1. Obvious mistakes in the description, claims or drawings, abstract, or any paper submitted to the IPEA are rectifiable before the IPEA (Rule 91.1 is not appropriate, before the IPEA, for rectifications to the request form, which are considered under Rule 92 bis). [Rule 91.1]
  2. Rule 26.4 specifies the manner in which rectifications are requested. [Rule 91.2]
  3. Where rectifications authorised by the IPEA involve a replacement sheet, copies of the replacement sheets must be annexed to the IPE Report. [Rule 66.8(a) Rule 70.16 Ad. Inst. 607].  The cover sheet of PCT/IPEA/409 is to indicate the presence of the annex or annexes. Box 1 of PCT/IPEA/409 is to indicate as “originally filed/furnished”.
  4. Rule 91.1(c) to (g) is the only source of instruction when considering requests for rectification i.e. case law does not exist.
  5. Although Rule 91.1(h) allows the IPEA to invite rectifications it is not envisaged that such invitations will be issued since any mistakes which can be rectified under Rule 91 will not cause any problems in establishing the IPRPII.

For guidance on the nature of an “obvious mistake”, see 6.1.17 Rule 91 Obvious Mistakes in Documents.

Amended Reasons

Amended Reason Date Amended

Published for testing

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